Upper panel: unfolded XRT data (in black) and average BAT spectrum (in blue) fitted including a Gaussian absorption line (E ~ 7.8 keV, EW ~ −230 eV and σ _E ~ 190 eV). The continuum (red continuous line) is modelled with an absorbed plus an unabsorbed power law and a reflection component. Lower panel: relevant residuals, plotted in terms of sigma with error bars of size one.